This invention relates generally to hinges and more specifically to a separable hinge having a self retaining hinge pin.
Numerous applications exist where it is necessary or highly desirable to join parts by means of a hinge and thereby permit motion therebetween in one plane, while at the same time having the capability of quickly and easily separating the parts by simply removing the hinge pin. For example, in some aircraft it is desirable to hinge the various control surfaces, such as the aelerons, rudder, elevator, flaps, trim tabs, engine exhaust nozzle flaps and the like, to adjacent structure in a manner whereby such control surfaces can be easily removed for inspection, repair or replacement. One of the problems, however, which must be assuredly avoided in the application described above is the unexpected separation of the hinged parts due to the falling out or working out of the hinge pin as a result of gravitational or other axial forces acting thereon.
As mentioned in U.S. Pat. No. 3,497,906 issued to E. J. McFadden on Mar. 3, 1970, various means are presently known to retain a hinge pin in a hinge pin bore, such as by riveting the hinge pin in place, by upsetting the surrounding portion of the hinge pin bore, by enlarging the end of the hinge pin by heating and peening, by threading a closure plug into the end of the hinge pin bore above the hinge pin, by threading the hinge pin and bore and passing a cotter pin through the hinge pin and adjacent hinge element to prevent unthreading of the hinge pin, or by extending a hinge pin through the hinge pin bore and placing a nut or other retaining means on the end thereof.
There are many objections and drawbacks to the above-mentioned means for retaining a hinge pin in a hinge pin bore. For example, because of the high tensile strength and hardness of the hinge material and the hinge pin material, threading or perforating thereof is a difficult and expensive operation. Heating the hinge pin or the surrounding hinge material for peening into position is undesirable because of the deleterious effect on the materials involved. Nuts have a tendency to work loose, and cotter pins wear through or are sheared off. Furthermore, heavy blows or jars may loosen and dislodge such fastening means.
McFadden in his patent, supra, discloses and claims yet another arrangement for retaining a hinge pin in place, which arrangement is suitable for his particular application. He discloses a hinge wherein a lock-bar, greater in length than the diameter of the hinge pin, is positioned chord-like in a slot across the end of the hinge pin, with the lock-bar extending into recesses located on opposite sides of the hinge pin bore and extending radially outward from the bore. This arrangement necessarily requires the use of an additional pin retaining device in the form of the aforementioned lock-bar, which can be easily lost and is not easily removed once installed in the hinge bore.
As for additional prior art devices which pertain to separable hinges, U.S. Pat. No. 1,372,242 issued to E. Mepsted on Mar. 22, 1921 discloses a locking type pin which may be used with hinges or the like. The pin itself has an eccentric bore therethrough. A locking member which extends through the bore has an enlarged cap or head on one end, and a radial locking projection located in a groove in the shank end of the pin. When the cap is turned or twisted, the radial locking projection is caused to extend beyond the shank end of the pin to a sufficient extent to secure the pin in position.
There are also hinge mechanisms which permit hinged parts to be quickly connected or disconnected by rotation of one hinge part ninety degrees (or some other angle not reached during normal operation of the hinge) with respect to the other hinged part. Such mechanisms generally comprise a hinge pin secured to one hinged part, and slots formed in the wall of the hinge pin bore in the other hinged part. The pin has one or more flats or detents which will fit through the slots when the hinge parts are at a specified angle with respect to one another. Such hinge mechanisms are shown in U.S. Pat. No. 2,926,382 issued to R. H. Knese et al on Mar. 1, 1980, and in an advertisement entitled "DE-HINGE" which appears on page 41 of Model Aviation Magazine, Vol. 10, No. 4, Apr. 1984. It is apparent that the presence of such slots in the wall of the hinge pin bore detract from the strength of the hinge and can adversely affect the durability and smoothness of operation of the device.
Therefore, all of the previously known hinge devices have serious limitations, some having their members permanently joined, some requiring the use of extra securing hardware, such as nuts, washers, cotter pins, locking bars and the like to retain the hinge pin, and yet others lacking strength or durability or being difficult and expensive to manufacture.